We studied urine excretion and plasma electrolytes in 38 rabbits during and after a 60-min intravenous infusion of 150 ml/kg of irrigating fluid containing either 3.3-6% of mannitol, 5% sorbitol, or 2.7% sorbitol and 0.54% mannitol (Cytal). The Osmolality of the solutions ranged between 165 and 350 mosmol/kg. The excreted urine volume, peak flow rate, duration of 80% of peak urine flow and the ... [Show full abstract] ratio of urine excreted per volume of infused irrigating fluid varied greatly but in direct proportion to the osmolality of each solution. There were no differences between the irrigating fluids with respect to dilution changes in plasma sodium and chloride concentrations. We conclude that the urine flow after infusion of irrigating fluids is governed primarily by the osmolality of the solution. Mannitol has no superior effect over sorbitol as a diuretic.